To provide a power-supplying device for slide door that can avoid an electrical connection failure and an electric shock.

The power-supplying device for a slide door comprises the first connector 30 which a holder 32 for holding terminal 31 is mounted to a car body and the second connector 40 which a holder 42 for holding terminal 41 is mounted to a slide door 2 and the terminals 31, 42 of the connectors 30, 40 are electrically connected with each other by closing the slide door 2, a cover 33 for covering the terminal 31 is mounted at the holder 32 of the first connector to be opened and closed. The cover 33 is closed when the slide door 2 is opened. If the slide door 2 is closed, both holders 32, 42 of both connector 30, 40 are coupled with each other and the cover 33 is opened.